1. Field of Invention
The present invention relates to an image display device and a projector. More particularly, it relates to a projector to illuminate a spatial light modulator, such as a liquid crystal light valve or a tilting mirror device with illumination light emitted from a light source, and to display an image by projecting the illumination light from a projection lens onto a screen or the like by causing the illumination light modulated by the spatial light modulator to impinge on a projection lens. Specifically, this technology is useful in displaying moving pictures.
2. Description of Related Art
FIG. 18 shows a conceptual schematic illustrating a related art projector. This projector 1000 is provided with a light source 110, a pair of fly-eye lenses 1021 and 1022, a superposing lens 1023, a collimating lens 140, a light valve 151, and a projection lens 160.
The fly-eye lenses 1021 and 1022 are lens arrays in which micro lenses having a rectangular form are arranged in the form of matrix. The external shape of each of the micro lenses is substantially similar to the external shape of the image-forming area of the light valve 151, serving as a spatial light modulator, when each of the micro lenses is viewed along the optical axis direction. For example, if the external shape of the image-forming area of the light valve 151 is a rectangular shape having an aspect ratio of 4:3, the external shape of each of the micro lenses also has a rectangular shape having an aspect ratio of 4:3.
The fly eye lens 1021 divides the illumination light emitted from the light source 110 into a plurality of partial light beams and condenses each of the divided partial light beams on the micro lenses of the fly eye lens 1022, respectively. The fly eye lens 1022 emits each of the plurality of divided partial light beams, and causes each of the emitted plurality of divided partial light beams to impinge on the superposing lens 1023. Further, the superposing lens 1023 superposes the plurality of split partial light beams after passing through a collimating lens 140, and then illuminates the superposed light beams on the image-forming region of the light valve 151. At this time, since the aspect ratio of each of the external shapes of the micro lenses and the aspect ratio of the image-forming area of the light valve 151 are equal to each other, illumination light having a uniform luminance distribution over the whole image-forming area of the light valve 151 can be generated.
Therefore, the projector 1000 illuminates the image-forming area of the light valve 151 with the illumination light emitted from the light source 110 by making the distribution of the luminance uniform, and after the illumination light is modulated by the light valve 151, the illumination light is incident on the projection lens 160 serving as the projection device, and then is projected from the projection lens 160 onto a screen (not shown) as image light, thereby displaying an image having smaller brightness irregularity.
Further, there is a liquid crystal light valve in which a liquid crystal panel is used in a single light valve. The projector illuminates the liquid crystal light valve with the illumination light emitted from the light source, the illumination light is modulated by the liquid crystal light valve based on the image signal, and the display performance of the moving picture to be projected onto the screen by the projector is equal to the display performance of the moving picture based on the response performance of the liquid crystal light valve, since the illumination light is projected onto the screen after expanding the illumination light by the projection lens.
Further, in the related art image display device, a technique to improve the quality of the moving picture has been proposed by scanning the illumination area to be illuminated by the display element. In a certain image display device, a construction for scanning the illumination area to be illuminated by the display element by disposing a plurality of light sources on the rear surface of the display element and sequentially turning the light on and off at predetermined time intervals is well known (for example, refer to Japanese Unexamined Patent Application Publication No. 2000-275604). Further, in another related art image display device, a construction for scanning the illumination area to be illuminated by the display element by rotating a light condensing tube provided with a slit for defining the direction in which the light source emits light is well known (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-6766).